1. The 2',3'-dialdehyde derivative of ADP (oADP) at concentrations approaching the millimolar range induces human blood platelets to undergo the transition from discoid to globular morphology (the 'shape change') but is incapable of inducing aggregation.2. When incubated with platelets for 1 min before addition of the agonist, oADP acts as a competitive inhibitor of shape change and aggregation induced by ADP. Under these conditions secretion and hence aggregation induced by low concentrations of collagen ; and secretion and hence secondary aggregation induced by adrenaline, thrombin and vasopressin are also inhibited by this analogue. In addition, oADP stimulates the rate of primary aggregation induced by adrenaline and causes partial inhibition of primary aggregation induced by thrombin or vasopressin. When longer preincubation times are employed the extent of inhibition with respect to all agonists, except for high concentrations of collagen, is increased and the competitive character of the inhibition with respect to ADP is no longer apparent.3. Incubation of human platelets with the 2',3'-dialdehyde derivative of ATP (oATP) causes effects similar to those described for oADP except that the analogue neither induces platelet shape change, nor stimulates the rate of primary aggregation induced by adrenaline. In addition oATP fails to cause significant inhibition of platelet shape change induced by serotonin. The extent and character of inhibition caused by addition of oATP is not a function of the time of incubation.4. The 2',3'-dialcohol derivatives of ADP and ATP (orADP and orATP) effect the aggregation properties of human blood platelets in a manner generally resembling those observed for the 2',3'-dialdehyde analogues. However, orADP is only weakly effective in causing platelet shape change and stimulating the rate of primary aggregation induced by adrenaline and does not inhibit secretion induced by adrenaline, collagen, thrombin and vasopressin. The extent of inhibition by OI-ADP increases only slightly with increased time of incubation. 5.The data suggest that oADP acts as a partial agonist, and oATP as an antagonist, at the platelet ADP receptor, but that platelet membrane stabilisation also results from interaction with these dialdehyde analogues. Such membrane stabilisation does not complicate the interaction of platelets with orADP, which appears to act as a classical antagonist for the ADP receptor.Many agonists are capable of inducing platelet aggregation including adrenaline, thrombin, vasopressin and serotonin. In citrated plasma and under suitable conditions these agonists induce a biphasic response in which only the first, or reversible, phase is the direct result of platelet-agonist interaction. This initial interaction causes secretion of platelet constituents some of which are themselves inducers of aggregation and hence cause a further response associated ~~ -~ Ahhwviu/iorw. oATP and oADP. the 2',3'-dialdehyde derivatibe of ATP and ADP; orATP and orADP, the 2',3'-dialcohol derivative of AT...

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It is only very recently that literary critics and historians have been faced with the new phenomenon of Aboriginal writing in what have been traditionally their fields. The question of what critical standards they are to apply to this new literature and history is a thorny one, and has already become something of a battleground.The 'literature of protest' in Western terms has of course a long history of its own. Minorities, and individuals, who feel themselves oppressed by the dominance of elements in their own society have often been able to express that sense within the literary modes and conventions of that society. But in the case of Aboriginal writers -part of an indigenous enclave of people within a society whose standards and criteria, as well as language, they may not feel the slightest compulsion to take as models -something new faces the critic working within his or her own literary tradition and culture. For the critic of today, a new tenderness of conscience may demand a questioning of critical method and a new look at literary styles and standards as they may be seen by the writer working wholly outside the acceptations of Western culture.Some critics and reviewers have chosen to stick to their lasts and speak de haut en bas as the standard-setters of a culture to which these new contributors must submit themselves. They apparently feel themselves unable, even unwilling, to accept a need to evolve a different aesthetic and critical method to take account of the aims, strengths and limitations of in digenous protest writing. They would presumably insist that an established literature and a language impose their own necessities, and that judgements can only be made in the terms they have laid down. But it is an uneasy position, and one that a colonising culture such as ours is increasingly forced to question.By what divine right have we established our own critical standards? Our long traditions of critical writing, for instance about poetry or the novel or the short story, are adapted to deal with the conditions and traditions of a social development very different from any milieu which Aboriginal writers live in or have to draw upon. And they are brief indeed when compared with the traditions of Aboriginal language, oral literature, oral history, evolved within a wholly different world-picture -one moreover which we have ignorantly despised and in most cases and places destroyed altogether. Can we apply the critical stand ards we use in evaluating new contributions to our own literature by those who inherit and live within the dominant culture and language, to those who have had no such education, training and background -and who, moreover, may bitterly and thoroughly reject all the bland assumptions of that culture and feel that language an alien imposition?Honest critics may have to admit that the tools of their trade -their education in linguis- 24